EP0012668A1 - Hydroelectric plant - Google Patents

Abstract

In a low-head hydroelectric power station, a turbine runner is mounted within the hub of a convergent-divergent draft tube at the base of a dam. At least one turbine is coupled to one or more electric generators housed within a casing which is totally submerged within the upstream pool. The distance from the generator casing to the draft tube intake is sufficient to prevent any interference with the water flow. The casing is provided with a vertical access and inspection shaft, the top opening of which is located above the normal water level and removably fixed on a flooring structure.

Description

The present invention relates to a low-drop hydroelectric plant.

Such plants generally include a dam separating an upstream reach and a downstream reach from a watercourse. In a pipe formed at the base of the dam is located a turbine mechanically connected to the shaft of an electric generator, generally by means of a speed multiplier.

In low-fall power plants, the location to be given to the generator presents a certain difficulty due to the low height of the dam to which we cannot give the masonry extensions sufficient to accommodate this machine. It has been envisaged to place it downstream of the dam, on a special structure, but this results in a significant civil engineering cost, and the flow of water downstream is thereby partially hampered.

One known solution consists in using a bulb group, in which the generator is enclosed in a profiled casing substantially of revolution around the common axis of the turbine and of the generator. The turbine is located at the tip of the casing, the assembly having a hydrodynamic profile studied to avoid detachments of the boundary layer and vortices.

A chimney opening into the open air permanently ventilates the generator and allows a man to descend inside the casing for maintenance purposes. It rises above the flood level.

In bulb groups of a certain size, corresponding to high water flows, the transverse dimensions of the chimney are small compared to those of the bulb, so that the water flow in the annular pipe around the bulb is only slightly disturbed. It is quite different with small groups, intended to treat low water flows, in which the section of the chimney is of the order of magnitude of the section of the bulb. We are then forced to resort to other solutions such as that mentioned above, or that of housing the generator in a gallery formed in the mass of the dam, which, among other disadvantages, constrained to give the flow channel sinuosities generating pressure losses.

The present invention aims to produce a hydroelectric power station which, even in the event of a low drop and of low flow, is of simple and economical construction without causing any significant pressure drop upstream or downstream of the turbine.

According to the invention, the low-drop hydroelectric power station comprises a dam which spares an upstream reach and a downstream reach on a watercourse, at least one turbine located in a channel formed at the base of the dam, and at least an electric generator connected to the turbines housed in a completely submerged enclosure. It is characterized in that this enclosure is located in the forebay, at a distance from the dam and the turbine, and upstream from the water speed-up zone, this enclosure comprising a visit chimney opening to the -above the normal water level and being fixed on a raft in a removable and removable manner.

Because of the sufficient distance, it is possible, without disturbing the flow, to give the enclosure relatively large dimensions, allowing easy access to the machines, and to provide it with an access chimney of reasonable dimensions.

In addition, the removable and removable nature of the enclosure and its contents makes it possible to completely assemble this assembly in the factory, reducing the assembly work on site. It is also possible, during operation, to dismantle the assembly to carry out a repair on the bank of the watercourse.

In many cases, the flow conditions are such that it is sufficient for the enclosure to be entirely located at a distance from the turbine at least equal to twice the diameter of the turbine wheel. It is exceptional that one is obliged to give this distance a value greater than ten times the diameter of the wheel.

According to a preferred embodiment of the invention, the generator is mechanically connected to the turbines by respective devices with 90 ° angle bevel, so that the shaft of the generator is substantially horizontal and perpendicular to the direction of flow of water in the stream.

It is known that the shaft of the turbine generally has a certain inclination downstream, in particular so that the conical diffuser of the turbine is always in charge. Thanks to the arrangement indicated, the double advantage is obtained of a reduced axial size and of a horizontal position of the generator shaft, which gives it a mechanically satisfactory balance.

In the relatively frequent case where a speed multiplier is necessary, the invention advantageously provides for combining this multiplier with the bevel gear device.

According to an advantageous embodiment of the invention, the plant comprises several turbines, the shafts of which are each connected to a bevel gear device, the output shafts of these devices being arranged in coaxial pairs and mechanically connected to the generator shaft.

This arrangement is particularly advantageous in the case of low-fall power plants, where the admissible diameter for the water pipe is limited, and where, consequently, the power of each turbine is also limited. The invention then makes it possible to group several of these turbines on the same more powerful generator accompanied by a single control cabinet.

According to an improved embodiment of the invention, the coaxial shafts of the bevel gear devices are connected to the generator shaft by means of a speed variator, so as to be able to maintain a constant speed of the generator. despite varying hydraulic conditions.

Still in the case of two turbines coupled to the same generator, each angle gear device is provided, on its output shaft, with a clutch device.

One of the two turbines can then easily be put into service or out of service without having to stop the operation of the power plant.

According to a preferred embodiment of the invention, the power station comprises a movable shutter valve for the water pipe in the dam, this valve being slidably mounted on the shaft of the turbine and actuable by control means fixed to the enclosure.

This closure device is both less expensive and more reliable than adjustable blades, the remote control of which is also expensive and complex.

According to the invention, the valve control means comprise hydraulic cylinders fixed to the enclosure, that is to say an economical device and robust.

As a safety measure, the cylinders include springs arranged to apply the valve to the pipe, in the event of a lack of hydraulic fluid pressure.

According to an advantageous improvement of the invention, there is provided a tube fixed to the enclosure, coaxial with the shaft of the turbine, to serve as support for the valve in the open position of the latter.

In the open position, the valve no longer has support on the seat. The aforementioned device provides this support to prevent it from entering into vibration.

According to a preferred embodiment of the invention, the inspection chamber comprises a sealed airlock.

The chimney can be accidentally submerged, for example during the strongest floods, without damage to the machines contained in the enclosure. We can therefore build relatively low chimneys, preserving the sites.

According to an important improvement of the invention, the airlock is in communication with a submerged bell, the lower edge of the skirt is located approximately at the entrance to the turbine shaft in the enclosure.

Thanks to this arrangement, there is a permanent pressure in the airlock which increases with the immersion height and which helps to prevent water infiltration into the enclosure in the event of accidental leaks.

According to a preferred embodiment of the invention, the enclosure comprises a double envelope, and fans are fixed on the shafts of the rotating machines to circulate the air in the double envelope.

Sufficient convection is thus obtained on the outer envelope of the enclosure to limit the temperature inside.

In an improved embodiment of the invention, a water refrigeration battery is provided located in the enclosure on the air circulation path. This refrigeration battery can advantageously be connected by pipes to a heat recovery installation.

As a variant, or in combination, the enclosure comprises beams for supporting the rotating machines, these beams being hollow and in communication with the watercourse.

Other features and advantages of the invention will emerge from the detailed description which follows.

• - la figure 1 est une vue d'ensemble en coupe, en élévation, d'une centrale conforme à l'invention, suivant I-I de la figure 2,
• - la figure 2 est une vue en plan en coupe suivant II-II de la figure 1,
• - la figure 3 est une vue en élévation, analogue à la figure 1, mais à plus grande échelle, suivant III-III de la figure 2,
• - la figure 4 est une vue en coupe suivant IV-IV de la figure 3,
• - la figure 5 est une vue analogue à la figure 4, mais dans une forme de réalisation à une seule turbine,
• - la figure 6 est une vue en coupe en élévation semi-schématique montrant la cloche adjointe au sas,
• - la figure 7 est une vue en coupe en plan semi-schématique montrant la double paroi de l'enceinte,
• - la figure 8 est une coupe suivant VIII-VIII de la figure 7,
• - la figure 9 est une vue en coupe en élévation, semi-schématique, montrant l'installation d'une batterie de réfrigération,
• - la figure 10 est une vue en coupe transversale semi-schématique montrant l'installation d'une poutre creuse,
• - la figure 11 est une vue de détail montrant la réalisation de la double paroi.

In the appended drawings, given by way of nonlimiting examples:

• FIG. 1 is an overall view in section, in elevation, of a power station according to the invention, along II of FIG. 2,
• FIG. 2 is a plan view in section along II-II of FIG. 1,
• FIG. 3 is an elevation view, similar to FIG. 1, but on a larger scale, along III-III of FIG. 2,
• FIG. 4 is a sectional view along IV-IV of FIG. 3,
• FIG. 5 is a view similar to FIG. 4, but in an embodiment with a single turbine,
• FIG. 6 is a semi-schematic sectional elevation view showing the bell attached to the airlock,
• FIG. 7 is a view in section in semi-schematic plan showing the double wall of the enclosure,
• FIG. 8 is a section along VIII-VIII of FIG. 7,
• FIG. 9 is a sectional elevation view, semi-schematic, showing the installation of a refrigeration battery,
• FIG. 10 is a semi-schematic cross-sectional view showing the installation of a hollow beam,
• - Figure 11 is a detail view showing the embodiment of the double wall.

With reference to FIGS. 1 to 4, the hydroelectric power station in accordance with the invention comprises a dam 1 defining an upstream reach 2 and a downstream reach 3 on a watercourse.

In the pipes 4a, 4b, formed at the base of the dam are housed respective turbines 5a, 5b, the wheels 6a, 6b of which are wedged on the respective shafts 7a, 7b.

Each shaft 7a, 7b is carried, on the one hand, by a bearing 8 with a rubber pad, mounted in the center of a star distributor 9 and, on the other hand, by a bearing 11 located inside an enclosure 12 into which the shaft enters via a sealed packing 13.

The enclosure 12 is made of sheet metal, supported by feet 14 resting on a raft 15 and entirely submerged in the forebay 2. The raft 15 is entirely independent of the structure of the dam 1, and the feet 14 are provided for being removable from this raft , for example by fixing with bolts. The enclosure 12 is located at a sufficient distance from the wheels 6a, 6b of the turbines so that the disturbance that its presence creates in the flow of water is negligible at the wheel level. In the example described, the enclosure is entirely located at a distance d from the wheels, a little more than twice the diameter of the largest of these wheels, in a region where the speed of water is that of the course of the course d upstream water.

In the example described, the enclosure 12 is cylindrical, of horizontal axis and parallel to the dam, and its diameter is approximately two meters, to allow a man to easily come to visit the machines.

In the enclosure 12, each of the shafts 7a, 7b is coupled to the input shaft of a speed multiplier 16a, 16b resting on a floor 17. The respective output shafts 18a, 18b of the multipliers are at 90 ° input shafts, so as to form angle references.

These output shafts are also coaxial (fig. 4), and coupled by clutch devices 19a, 19b to a common intermediate shaft 21 constituting the input shaft of a variable speed drive 22 with V-belts, of which the output pulley 23 is wedged on the shaft of an electric generator 24 placed on a floor 25.

There is shown in Figure 5, an alternative embodiment in which the plant comprises only one turbine.

The single shaft 7 is connected to a multiplier 16, the output shaft of which drives a variable speed drive 22, the output pulley 23 of which is fixed on the shaft of an electric generator 24.

In both cases, it follows from the structure described that the generator shaft is substantially horizontal and perpendicular to the direction of flow of the water in the watercourse.

Each of the trees 7a, 7b, is contained in a coaxial tube 26, fixed at each end respectively to the distributor 9 of the pipe and to the enclosure 12. This tube is pierced with holes along its lower generatrix, so that the water can circulate there freely. The seal 13 mentioned above is precisely fixed on the end of the tube 26 which enters the enclosure 12. A valve 27 coaxial with each tube 26 is slidably mounted on the tube by suitable means, such as bearings 28 This valve is in a spherical cap, of a diameter such that it can be applied to the nozzle 28a, 28b of the turbine inlet to close it in position 27a. To this end, it includes a peripheral rubber seal 29.

Two twin jacks 31 located in the enclosure 12 and parallel to each of the shafts 7a, 7b have their rods 32 fixed to the valve 27 and their bodies 33 fixed to the enclosure 12. For greater clarity, these jacks have not been shown. as in Figure 5. Their stroke is such that they can move the valve 27 between its closed position 27a and its open position 27. They are connected, by pipes not shown, to a source of pressurized hydraulic fluid by l '' through control valves. In addition, they each comprise a spring 34 which tends, in the event of a lack of pressure of the hydraulic fluid, to bring the valve 27 into the closed position 27a.

A tube 35, coaxial with each shaft 7a, 7b is fixed on the enclosure 12 and has a diameter equal to the diameter of the valve 27 to receive the latter in support in its open position.

An access chimney 36 is fixed to the enclosure 12 and rises to a certain height above the normal level of the water in the forebay 2. This chimney has a tight lid 37 at its part upper and another sealed cover 38 in the vicinity of the enclosure 12, so as to provide a sealed airlock 39 between these two covers. Steps 41 allow staff to descend into the enclosure 12 from an access floor 42.

Cable glands 43 and 44 placed respectively in the wall of the chimney and in a fixed part of the cover 38 allow the output of the electrical connection cables 45.

In an improved embodiment of the invention, indicated here as a variant (FIG. 6), a submerged bell 46, open at its lower part, is fixed against the dam 1 and communicates by a pipe 47 with the chimney 36. The lower edge of the bell 46 is located approximately at the entrance to the shafts 7a, 7b, in the enclosure 12.

The electric lines 45 take the line 47 and exit by a bypass 48 from this line.

A valve 49 on the pipe 47 makes it possible to isolate the bell from the airlock when the latter is opened. Finally, line 48 is connected to a source of compressed air, not shown.

The enclosure 12 comprises (FIGS. 7 and 8) an outer casing 51 and an inner casing 52. Pipes 53, 54 are provided in the inner casing 52 and the rotating machines 16a, 24 are housed in cavities 55, 56 located on the course of these pipes. Each of the machines is provided with a fan 57 to circulate the air in the interval between the envelopes, in a closed circuit.

The inner envelope 52 is fixed to the outer envelope 51 by means of corrugated sheets 58 (FIG. 11), or by means of ribs.

According to an alternative embodiment of the invention (FIG. 9), a water refrigeration battery 59, connected to the outside by circulation pipes not shown, makes it possible to recover part of the heat given off by the machines.

According to another alternative embodiment of the invention, certain beams on which the floors 17 and 25 supporting the rotary machines rest are formed by tubes 61 communicating with the upstream reach and giving rise to a circulation of water.

We will now explain the operation of the installation thus described.

The valve 27 being open on the two nozzles 28a, 28b, the water flows into the turbines and rotates the shafts 7a_, 7b to actuate the generator 24 by means of the multipliers 16a, 16b of the common shaft 61 and drive 22.

Given the relatively large distance between the enclosure 12 and the nozzles, the current disturbance caused by the presence of the enclosure is completely absorbed at the nozzles. This disturbance is itself very low, moreover, because the enclosure 12 is located in a region where the speed of the water is low.

The speed controller 22 is adjusted to obtain the desired speed on the generator 24, according to the hydraulic conditions at the time.

Depending on the available hydraulic reserve, or on the requested electric power, one of the two turbines can be put out of service or in service, thanks to the clutch devices 19a, 19b.

The height of the chimney 36 being limited to the floor 42 so as not to harm the site, the latter can be submerged during the highest floods. Thanks to the two waterproof covers 37 and 38, water does not invade the enclosure, and the only consequence of floods is to prevent the machines from being visited for a relatively short time.

During normal level, access to the machines is easy because of the relatively large dimensions that can be given to the chimney and the enclosure, without risk of disturbing the flow in the nozzles for the radiations explained above.

The embodiment of FIG. 6 corresponds to the case where it is wished to guard against any infiltration of water coming, for example, from an accidental leak at the seal 13. The back pressure coming from the bell and s exerting at the level of the packing obstructs the entry of water.

A leak through the covers 37 and 38 may give rise to a slight accumulation of water at the bottom of the enclosure, which is unimportant because of the large dimensions of the latter. If the water level in the enclosure exceeds the level of the lining 13, the overpressure will tend to expel this water through the lining.

Air leaks which could eventually occur in the whole of the bell and airlock can be compensated by an injection of compressed air.

Of course, when the airlock is opened, the valve 49 should be closed beforehand to avoid the rise of water in the bell 46.

When the machines are running, the fans 57 circulate the air between the outer casing ₅ 1 and the inner casing 52, which provides sufficient heat exchange between the air and the outer wall 51 to maintain the interior of the enclosure at a sufficiently low temperature, the heat produced being finally evacuated to the river.

In the embodiment of FIG. 9, the water cooling battery makes it possible to recover the heat released, for example for the heating of service rooms.

The water tubes 61 (fig. 10) further improve cooling by providing an additional cold surface.

Finally, the invention advantageously provides for having in the enclosure 12 a bilge pump (not shown) in order to evacuate the water coming in particular from accidental infiltration.

The invention solves the problem of exploiting very low falls by overcoming the small space available. The installation of the machines and their means of access can be relatively bulky without disturbing the flow. In addition, the use of 90 ° angle controls allows, on the one hand, to easily connect two turbines to the same generator and, on the other hand, to have the overall dimensions of the assembly according to the width of the stream, that is to say without requiring the layout of the stream, along a great length, and without increasing the overall height.

Civil works are minimized, and assembly is simple. Due to the lightness of the material, it can, to a large extent, be assembled and assembled in the factory, then transported all assembled on the site where it only remains to install it.

Conversely, the possibility of dismounting the feet 14 provided above makes it possible, in the event of a major disturbance, to remove the entire assembly from the water in order to carry out a repair on the bank of the watercourse at leisure.

The dispenser 9 is easily accessible while in operation and can be easily rid of foreign bodies which may block it.

Another important advantage of the invention is linked to the fact that it is possible to couple several turbines of reduced diameter on the same generator. This reduction in diameter, in addition to making it possible to operate at very low heights of fall, makes it possible moreover to increase the speed of the turbines, therefore to decrease the torque and also to decrease the ratio of the speed multiplier.

Of course, the invention is not limited to the examples described, but covers any constructive variant within the reach of ordinary skill in the art, in particular those which have been indicated in the description.

One can for example couple more than two turbines to the same generator. In the case of four turbines, the four speed multipliers are grouped, two by two, each pair having its coaxial output shafts. Two variable speed drives are then used, themselves coupled to the turbine shaft.

Claims (17)

1. Low-fall hydroelectric power station, comprising a dam which spares an upstream reach and a downstream reach on a watercourse, at least one turbine located in a speeding-up water pipe at the base of the dam, and at least one electric generator connected to the turbines housed in a completely submerged enclosure, characterized in that this enclosure is located in the forebay, at a distance from the dam and the turbine, and upstream from the speed-up zone of water, this enclosure comprising an inspection chimney opening above the normal level of water and being fixed on a raft in a removable and removable manner. 2. Hydroelectric plant according to claim 1, characterized in that the enclosure is entirely located at a distance from the turbine at least equal to twice the diameter of the turbine wheel. 3. Hydroelectric power station according to one of claims 1 or 2, characterized in that the generator is mechanically connected to the turbines by respective devices with 90 ° angle transmission, so that the generator shaft is substantially horizontal and perpendicular to the direction of flow of the water in the watercourse. 4. Hydroelectric power station according to claim 3, characterized in that the angle transmission device comprises a speed multiplier. 5. Hydroelectric power station according to one of claims 3 or 4, characterized in that it comprises several turbines, the shafts of which are each connected to a device with angle gear, the output shafts of these devices being arranged in coaxial pairs and mechanically connected to the generator shaft. 6. Hydroelectric power station according to claim 5, characterized in that the coaxial shafts of the bevel devices are connected to the generator shaft by means of a speed variator. 7. Hydroelectric power station according to one of claims 5 or 6, characterized in that each angle gear device is provided, on its output shaft, with a clutch device. 8. Hydroelectric power station according to one of claims 1 to 7, characterized in that it comprises a movable shutter valve for the water pipe in the dam, this valve being slidably mounted on the shaft of the turbine and actuable by control means fixed to the enclosure. 9. Hydroelectric power station according to claim 8, characterized in that the valve control means comprise hydraulic cylinders, fixed to the enclosure. 10. Hydroelectric power station according to claim 9, characterized in that the jacks comprise springs arranged to apply the valve to the pipe. 11. Hydroelectric power station according to one of claims 8 to 10, characterized in that it comprises a tube fixed to the enclosure, coaxial with the shaft of the turbine, to serve as support for the valve in position open of the latter. 12. Hydroelectric plant according to one of claims 1 to 11, characterized in that the inspection chimney comprises a sealed airlock. 13. Hydroelectric power station according to claim 12, characterized in that the airlock is in communication with a submerged bell whose lower edge of the skirt is located approximately at the entrance of the turbine shaft in the enclosure. 14. Hydroelectric power station according to one of claims 1 to 13, characterized in that the enclosure comprises a double envelope, and in that fans are wedged on the shafts of rotating machines to circulate the air in the double envelope. 15. Hydroelectric plant according to claim 14, characterized in that it comprises a water refrigeration battery located in the enclosure on the air circulation path. 16. Hydroelectric plant according to claim 15, characterized in that the refrigeration battery is connected by pipes to a heat recovery installation. 17. Hydroelectric power station according to one of claims 1 to 16, characterized in that the enclosure comprises beams to support the rotating machines, these beams being hollow and in communication with the watercourse.

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